HNU CS 计网期中仅供学习如有侵权联系作者删除第一部分-简答题10*4T1考点UDP校验和多路复用多路分解socket写出UDP的特征3UDP校验和要把什么内容加在一起3说明多路复用和分解复用的原理说明源套接字和目的套接字在其中的用途4T2考点网络边缘网络核心TCP/IP协议栈情景一云服务器厂商确保全国客户连接稳定快速不会因为一个服务器的瘫痪而全部瘫痪情景二公司内打印机笔记本台式机组网使其访问更快情景一二分别对应的是网络边缘还是网络核心阐述理由3网络核心网络边缘在TCP/IP协议栈的位置3指出网络边缘和网络核心的核心设计原则列举说明4(e.g., desktop PCs, Macs, and Linux boxes), servers (e.g., Web and e-mail servers),and mobile devices (e.g., laptops, smartphones, and tablets). Furthermore, anincreasing number of non-traditional “things” are being attached to the Internet asend systems (see the Case History feature).T3考点排队时延流量强度路由器缓存R7*10^5bps L2800bit排队时延和流量强度的关系3算d_queue假设a53pkt。给了公式d_queueIL/R (1- I)好像是但是遗忘。。。带进去算就行了3实际的流量强度和排队时延的关系4类似于P14. Consider the queuing delay in a router buffer. Let I denote traffic intensity;that is, I La/R. Suppose that the queuing delay takes the form IL/R (1- I)for I 1.a. Provide a formula for the total delay, that is, the queuing delay plus thetransmission delay.b. Plot the total delay as a function of L /R拓展P16. Consider a router buffer preceding an outbound link. In this problem, youwill use Little’s formula, a famous formula from queuing theory. Let Ndenote the average number of packets in the buffer plus the packet beingtransmitted. Let a denote the rate of packets arriving at the link. Let d denotethe average total delay (i.e., the queuing delay plus the transmission delay)experienced by a packet. Little’s formula is N a * d. Suppose that onaverage, the buffer contains 100 packets, and the average packet queuingdelay is 20 msec. The link’s transmission rate is 100 packets/sec. UsingLittle’s formula, what is the average packet arrival rate, assuming there isno packet loss?T4考点web缓存HTTP 304 not modifiedTCP三次握手RTT计算传输时延计算web安全cookie考虑C-S架构C现在向S请求70个对象对象30%在自己的缓存内给了dtrans RTT计算总传输时间因为有网络缓存如何确保自己上网的安全性第二部分 综合设计题20*3T5考点TCP协议 TCP序列号ACK号 TCP三次握手 TCP流量控制 快速重传 S-ACK 超时重传 累计确认 TCP拥塞控制 ECN考虑C-S结构。初始序列号C1000 、S2000UDP和TCP的差异为什么TCP是面向连接的可靠传输协议3TCP三次握手的过程写序列号5滑动窗口由哪两个参数决定接收方滑动窗口大小为0发送方怎么办min{rwnd,cwnd}4MSS500b 报文总共大小1000b 第一个报文段丢了剩下的到了描述TCP传输的过程4某电商平台双十一期间太多人下单导致网络拥塞如何控制吞吐量举例说明4T6考点DNSRTT计算三次握手持续/非持续HTTP并行连接类似于CNTDA第八版第二章课后习题P7. Suppose within your Web browser you click on a link to obtain a Web page.The IP address for the associated URL is not cached in your local host, soa DNS lookup is necessary to obtain the IP address. Suppose that n DNSservers are visited before your host receives the IP address from DNS; thesuccessive visits incur an RTT of RTT1, . . . , RTTn. Further suppose that theWeb page associated with the link contains exactly one object, consisting ofa small amount of HTML text. Let RTT0 denote the RTT between the localhost and the server containing the object. Assuming zero transmission timeof the object, how much time elapses from when the client clicks on the linkuntil the client receives the object?P8. Referring to Problem P7, suppose the HTML file references eight very smallobjects on the same server. Neglecting transmission times, how much timeelapses witha. Non-persistent HTTP with no parallel TCP connections?b. Non-persistent HTTP with the browser configured for 6 parallelconnections?c. Persistent HTTP?考虑C-S架构 C里面点击一个链接此链接的IP不在本地cache内不在本地DNS服务器内访问了2个权威服务器才找到。不过是3个DNS服务器 1本地rtt02 2权威DNSrtt133 rtt235 访问站点的rtthtp31单位都是ms得到链接后先请求1对象接下来请求对象中的5个引用对象对象大小很小忽略dtrans点击链接到得到IP地址的时间4点击链接到得到所有对象的时间非持续串行4同2非持续并行4同2持续并行4非持续串行、非持续并行、持续串行、持续并行哪个最好4补充T7考点TCP拥塞控制cwndssthreshTCP RenoTCP Tahoe慢启动拥塞避免快速恢复冗余ACK类似于这道题考试题目问法类似于a-g也是5个小题5*4难度略低于此题题目也有一张图但是很难画出来这里不给了
